Development of an Algorithm for an Automatic Determination of the Soil Field Capacity Using of a Portable Weighing Lysimeter

The challenge today is to optimize agriculture water consumption and minimize leaching of pollutants in agro-ecosystems in order to ensure a sustainable agriculture. The use of different technologies and the adoption of different irrigation strategies can facilitate efficient fertigation management. In this respect, the determination of soil field capacity point is of utmost importance. The use of a portable weighing lysimeter allows an accurate quantification of crop water consumption and water leaching, as well as the detection of soil field capacity point. In this work, a novel algorithm is developed to obtain the soil field capacity point, in order to give autonomy and objectivity to efficient irrigation management using a portable weighing lysimeter. The development was tested in field grown horticultural crops and proved to be useful for optimizing irrigation management.

Characterization of the Transpiration of a Vineyard under Different Irrigation Strategies Using Sap Flow Sensors

Lysimeters are the reference method for determining ETc, but they are expensive and complex, which limits their use. The first objective of this work was to adjust and evaluate the robustness of sap flow sensors in order to determine the transpiration of a vineyard and, together with an evaporation model, to calculate the ETc of the vineyard. For this purpose, we compared water consumption data obtained from a vineyard weighing lysimeter (ETcLys) with the sum of transpiration obtained from sap flow sensors (TSF) and evaporation estimated empirically over four years (2012, 2013, 2014 and 2015). The second objective was to obtain the relationship between the vegetative growth and transpiration of the vines with different water availability (irrigation and rainfed treatments), as an alternative method for estimating vine water needs adjusted to their real development. The third and last objective was to evaluate the transpiration response of the vines when subjected to water stress. We carried out the work in an experimental vineyard which has a well-established weighing lysimeter. As a result, a good match was obtained between vine sap flow and transpiration (R2 = 0.85) as well as a good relationship between vegetative growth and vine transpiration (FiPAR: R2Irrigation = 0.34. R2Rainfed = 0.54; LAI: R2Irrigation = 0.68. R2Rainfed = 0.53).

Standardization of the Dimensions of a Portable Weighing Lysimeter Designed to Be Applied to Vegetable Crops in Mediterranean Climates

The progress made in developing information and communication technologies (ICTs) and the fact that water resources are becoming increasingly scarce make precision agriculture a very valuable tool for efficient and sustainable crop management, particularly for irrigation and fertilisation. In line with this, the water balance estimate is considered one of the most accurate methods for estimating crops’ water requirements. The Agromotic Engineering and Sea Research Group of the Universidad Politécnica de Cartagena (Spain) has worked in this direction to obtain portable weighing lysimeters with improved functions compared to traditional measurement systems. This study analysed the most important vegetable crops in south-eastern Spain to standardise suitable dimensions so that these portable weighing lysimeters can monitor practically all of today’s vegetable and herbaceous crops in Mediterranean climates. The dimensions established for the cultivation tank are 150 cm long, 45 cm wide, and 50 cm deep, with an equipment resolution of up to 0.09 mm expressed as water lamina. The validation over seven irrigation events established that the structural system achieved here allows precise monitoring of the water exchanges produced in the cultivation tank, so this portable weighing lysimeter can be useful for the efficient management of fertigation.

A Compact Weighing Lysimeter to Estimate the Water Infiltration Rate in Agricultural Soils

Infiltration estimation is made by tests such as concentric cylinders, which are prone to errors, such as the lateral movement under the ring. Several possibilities have been developed over the last decades to compensate these errors, which are based on physical, electronic, and mathematical principles. In this research, two approaches are proposed to measure the water infiltration rate in a silty loam soil by means of the mass values of a lysimeter weighing under rainfall conditions and different moisture contents. Based on the fact that with the lysimeter it is possible to determine acting soil flows very precisely, then with the help of mass conservation and assuming a downward vertical movement, 12 rain events were analyzed. In addition, it was possible to monitor the behavior of soil moisture and to establish the content at field capacity from the values of the weighing lysimeter, from which both approach are based. The infiltration rate of these events showed a variable rate at the beginning of the rainfall until reaching a maximum, to descend to a stable or basic rate. This basic infiltration rate was 1.49 ± 0.36 mm/h, and this is because soils with fine textures have reported low infiltration capacity. Four empirical or semi-empirical models of infiltration were calibrated with the values obtained with our approaches, showing a better fit with the Horton’s model.

Estimation of the Evapotranspiration and Crop Coefficients of Bell Pepper Using a Removable Weighing Lysimeter: A Case Study in the Southeast of Spain

Water use efficiency is essential in semiarid regions of Spain, and it can be achieved through a precise knowledge of the real crop water requirements (CWR). The Food and Agriculture Organization of the United Nations (FAO) offers standardized crop coefficients to establish the CWR. However, these coefficients can change due to different conditions, such as climatic variations and cultivation practices. In this work, the evapotranspiration (ETClys) and crop coefficients (KClys) of bell pepper were obtained with a compact removable weighing lysimeter between February and August for two crop seasons (2019 and 2020). ETClys was determined from the water balance, and the KClys values were determined as the ratio of the crop evapotranspiration, measured on the removable weighing lysimeter, and the reference evapotranspiration. The KClys average values for the bell pepper in the initial, middle, and final stages were 0.57, 1.06, and 0.80, respectively. KC regression models were obtained as a function of the fraction thermal units, achieving a maximum correlation of 0.67 (R2). In general, the KC values obtained in this research work were lower in the initial and in the final stages and larger in the middle stage in comparison with the FAO-56 values and other research works values in semiarid conditions. The bell pepper yield increased by 7.72% in 2019 and by 3.49% in 2020 compared to the yield reported by the Ministry of the Environment and Rural and Marine Areas of the Spanish Government in 2019 and with a minimum water loss through drainage. The results in this work can help farmers to determine the crop water requirements and to improve the system efficiency in semiarid locations with similar conditions to those in the study.

CALIBRATION OF A WEIGHING LYSIMETER FOR MEASURING COCOA EVAPOTRANSPIRATION

ABSTRACT Well-operated and calibrated weighing lysimeters reliably determine the water demand of agricultural crops, and the quality of the data is evaluated through the error analyses attributed to the instrument. The objective of this study was to determine performance parameters of a weighing lysimeter and to evaluate its adequacy for the direct determination of cocoa crop evapotranspiration. The lysimeter with 1.44 m2 surface, supported on four load cells installed in the experimental area of the Graduate Program in Agricultural Engineering of the Universidade Federal do Recôncavo da Bahia, was calibrated at 3:00 a.m., using known masses at intervals of 02 minutes in five cycles of addition and removal. Data were collected using a datalogger coupled to four load cells with an individual capacity of 1000 kg, programmed to perform readings every 01 second, storing the averages of 15 minutes. The lysimeter showed excellent accuracy, with r2greater than 0.99 in the correlation between the standard masses and the signal of the load cells and standard error of linear regression estimate of 0.03 mm. The combination of repeatability and hysteresis errors with an uncertainty of 0.19% showed that the load cells have accuracy of ±0.07 mm, with resolution of 0.00033 mV, and sensitivity to detect mass changes below 0.1 mm, the system is adequate for direct measurement of cocoa ETc at time intervals of less than one hour.

Removable Weighing Lysimeter for Use in Horticultural Crops

Water resources management is a priority issue in agriculture, especially in areas with water supply problems. Recently, one of the most widespread technologies for measuring crop water requirements are weighing lysimeters. Nevertheless, this type of lysimeters are of large dimensions and require a civil work for their installation. In this article, we present a weighing lysimeter prototype (1000 × 600 mm and 350 mm depth) designed to be used in agricultural farming of horticultural crops. We described the design details that includes ease of assembly, carriage and minimum soil alteration. Structural design results and construction process are also provided showing their performance under different tractors scenarios. The measurements accuracy results show the outcomes of the prototype after being tested. Finally, we discuss our design and measurements results by comparing them with other weighing lysimeters. In comparison, the prototype designed is an accurate and reliable device which reduces the surface and depth of the current weighing lysimeters.

CONSIDERING SOIL WATER CONTENT, NUTRIENTS MOVEMENT, PHENOLOGY AND PLANT GROWTH WITH REFERENCE TO DEVELOPMENT OF FUNCTIONAL FOODS IN A LYSIMETER STUDY

Lysimeter is equipped with mechanisms for weighing by load cells enable automated measurements, and the signals resulting from weight changes in the system due to evaporation that are generally recorded in a data acquisition system. According to methods of measuring water content, lysimeters may be divided into weighing lysimeter and non-weighing lysimeter. The weighing lysimeters provide scientists the basic information for research related to evapotranspiration, and they are commonly divided into two types, continuous weighing and intermittent weighing. Weighing lysimeters have been used to quantify precipitation (P) not only in the form of rain or snow, but also dew, fog and rime, and also to determine actual evapotranspiration (ET). Compared to laboratory experiments, out-door lysimeter studies have advantages, like being closer to field environment conditions, it is possible to grow plants and therefore to study the fate of chemicals in soil/plant systems, transformations and leaching. The limitations are costy, which depend on design, variable experimental conditions, such as environmental/ climatic parameters, which are normally not controlled, the soil spatial variability is normally less, they are not suitable for every plant species and even every soil type. The objective of lysimeter is defining the crop coefficient (Kc), which used to convert ETr into equivalent crop evapotranpiration (ETc) values, and determing agronomical characteristics of crops, which are planted in the field of lysimeter. The duration of a lysimeter study is determined by the objective of the study, but for different crops, it should normally be at least two years. Weighing lysimeters using load cells have the advantage of measuring the water balance in the soil over a short time and with good accuracy. Precipitation should be recorded daily at the lysimeter site. All weather data like air temperature, solar radiation, humidity and potential evporation should be obtained onsite, and the frequency and time of measurements should be at least daily.